The objectives of the work in our laboratory are to purify some antibiotic-sensitive enzymatic reactions in bacterial cell wall synthesis and to study in detail the mechanism of inhibition of these enzymes by the relevant antibiotics. There are a number of enzymes and antibiotics which are of interest in this connection. Peptidoglycan transpeptidase catalyzes the terminal cross-linking of peptidoglycan strands. This reaction is inhibited by penicillins and cephalosporins. Disaccharide-peptide transferase catalyzes the polymerization of a linear peptidoglycan from a lipid intermediate in bacterial cell wall synthesis. This enzyme is inhibited by vancomycin and ristocetins. Lipid pyrophosphatase catalyzes the dephosphorylation of lipid pyrophosphate to lipid phosphate (the lipid is a C55-isoprenoid alcohol). This reaction is essential for the regeneration of the lipid carrier in the course of cell wall synthesis and it is inhibited by bacitracin.